Lab Tests.
Last updated Tuesday, January 04, 2005
Blood testsAbout blood tests A patient with arthritis will have probably more blood tests than any
other type of test because blood is the most easily and safely sampled
body tissue and contains traces of material from every other part of
the body. The most common blood tests include the following.Hematocrit (HCT) and hemoglobin (Hgb) counts These measure the number and quality of red blood cells. If you have
chronic inflammation, the number of red blood cells usually is low
(inflammation is a body process that can result in pain, swelling,
warmth, or redness). Low hematocrit and hemoglobin counts may be signs
that your medication is causing a loss of blood from your stomach and
passing through your bowel. Low counts also may indicate a decrease in
red blood cell production.
White blood cell count (WBC) WBC tests measure the number of white blood cells present. When you
have an infection, your body makes more white blood cells. Some
medications can decrease the number of white blood cells, which could
increase your chances of getting an infection.Platelet count This test measures the number of "sticky" cells or platelets that help
the blood to clot (aspirin and some other medications make the
platelets less "sticky"). If the number of platelets is low you could
have too much bleeding. Some powerful arthritis medications in rare
instances lower the platelet count.Erythrocyte sedimentation rate (ESR) This test, also called "sed rate," determines if you have inflammation.
The sed rate can measure the amount of inflammation present. The test
measures how fast red blood cells cling together, fall, and settle
toward the bottom of a glass tube in an hour's time, like sediment. The
higher the sed rate, the greater the amount of inflammation. As
inflammation responds to medication, the sed rate usually goes down.
This is an example of a test your doctor might order several times.
Another test used to measure this is the C-Reactive Protein (CRP) test.Salicylate level This measures the amount of salicylate in the blood to find out if
enough is being absorbed to reduce inflammation (salicylate is the main
ingredient in aspirin and some other NSAIDs).
This is a helpful test for people who are taking large doses of these
medications for a long time. High salicylate levels can be harmful,
with or without such symptoms as ringing in the ears, nausea, vomiting,
or even fever.Muscle enzyme tests (CPK, aldolase) These tests measure the amount of muscle damage (in some rheumatic
diseases, damaged muscles release certain enzymes into the blood).
These tests also can show how effective medication has been in reducing
inflammation that causes muscle damage.Liver enzyme tests (SGOT, SGPT, bilirubin, alkalin These tests measure the amount of liver damage. Certain medications used in the treatment of arthritis can damage the liver. Aspirin,
for example, has been known in rare instances to damage the liver,
especially in children or in people who have had previous liver damage.
Other NSAIDs can cause liver inflammation (hepatitis). Methotrexate can cause liver damage, especially in people who drink alcohol.Creatinine tests These measure kidney function. Creatinine is a normal waste product of
the muscles. A high level of it means that the kidneys are not working
well enough to remove waste products from the body.What are uric acid tests? These tests measure the amount of uric acid in the blood. People with gout
usually have high levels of uric acid, which forms into crystals that
are then deposited in the joints and other tissues. However, not
everyone with a high uric acid level has gout.
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